The present invention is related to a method of introducing an additive into a fluid system, as well as to a method for detecting leaks and an apparatus and composition useful for leak detection.
Daylight visible and ultraviolet fluorescent dyes have been used to detect leaks in refrigeration systems utilizing fluorocarbon refrigerants and refrigerant oils. Typically, these dyes are introduced into the refrigeration system, and at the site of the leak, the leaking refrigerant, oil and dye are detected under normal or UV light.
More specifically, a leak-detecting trace fluid, which is generally a fluorescence (powdered) dye material dissolved in an oil or petroleum fraction carrier, is introduced into the refrigeration system. The fluorescent dye material is carried throughout the system, and at the location of a leak, the refrigerant, oil, and fluorescent dye material leak into the atmosphere. The refrigerant is subsequently vaporized, leaving an oil residue containing the fluorescent dye material. Application of a UV light to this area results in the illumination of the oil/fluorescent dye material.
U.S. Pat. No. 1,915,965 discloses a leak detector method for a compression refrigeration system. Daylight visible compounds, such as methyl violet, crystal violet, auramine B, rhodamine E, etc. are introduced into such systems as leak detectors.
U.S. Pat. No. 4,249,412 discloses a UV fluorescent dye composition comprising water, a nonionic surfactant, a 1.0 wt. % sodium fluorescein and a semi-synthetic thickening agent. This fluorescent dye composition is sprayed on the external surfaces of a system where the bubbles formed by the leak fluoresce under UV light.
Other prior art examples include U.S. Pat. No. 4,369,120, which discloses anthraquinone blue dyes for use as visual leak detectors of refrigerants, refrigerant oils, and mixtures thereof; U.S. Pat. No. 4,758,366, which discloses a UV fluorescent dye composition comprising a polyhalogenated hydrocarbon refrigerant, a refrigeration oil, or a mixture thereof, with a fluorescent dye; U.S. Pat. No. 5,149,453, which discloses a UV fluorescent dye composition comprising an effective amount of a fluorescent, alkyl substituted perylene dye combined with a refrigerant oil and a polyhalogenated hydrocarbon refrigerant; U.S. Pat. No. 5,357,782, which discloses a UV fluorescent dye composition comprising an optical brightener mixed with either mineral oil, polyalkylene glycol or polyol ester refrigeration lubricant; U.S. Pat. No. 5,167,140, which discloses a method of introducing a fluorescent dye solution into a system with an atomizing mist infuser, wherein four different formulas for the fluorescent dye solution are disclosed, wherein the dye solution is a fluorescent dye mixed with an appropriate refrigerant oil; WO 92/07249, which discloses a method and a sensor system for detecting hydrocarbon-containing fluids by fluorescent detection, wherein additives used in hydrocarbon-based fluids, such as gasoline, heating oils and motor oils, can fluoresce, and can be used to detect and locate the source of ground water contamination from gasoline and oil storage tanks using a fluorescent sensor which detects the presence of fluorescing materials such as Coumarin 153.
Furthermore, U.S. Pat. No. 5,440,919, discloses a method of introducing a UV fluorescent dye additive into a closed refrigeration system by placing the fluorescent dye on a swatch of material installed in a desiccant bag which is placed in a dehydrator or filter (i.e. filter-dryer) of the refrigeration system. The swatch is capable of releasing as well as adsorbing the dye. The refrigerant and system lubricant flow through the dehydrator and are then mixed with the fluorescent dye, thereby allowing the fluorescent dye to be carried throughout the system. Although this system allows the introduction of the fluorescent dye into the system without requiring the use of a carrier oil, it also requires that the dehydrator or filter-dryer of the system be changed in order to introduce the dye into the system.
Generally speaking, the standard industry method of introducing daylight visible or fluorescent dyes into a refrigerant oil, has been to dissolve the dye in the refrigeration oil and to introduce this mixture into the system. There are however currently several different types of oils that are used in refrigeration systems. For example, polyalkylene glycol (PAG), polyol ester (POE), alkylbenzene (AB) and mineral oils are all used in current systems and some of these oils (or their additives) are incompatible with one another in concentrations as low as 1%. This means that a service technician must carry an inventory of all different types of fluorescent dye mixtures, i.e. one for each oil type.
An even greater problem with the conventional approach is that the technician must first determine which type of oil is used in the system which is being checked for leaks, as often, the technician is called upon to repair a leak in a system which has not been previously serviced and in which the oil used is unknown. This presents a significant problem. We have recognized that a more universal fluorescent leak check solution which is compatible with all potential lubricants and delivery method is needed to simplify leak detection in refrigeration systems.
The type of daylight visible or fluorescent material used for leak detection is also critical because the additives used in oils can interact with the material or the material could directly and negatively affect the properties of the oil or refrigerant. Although the quantity of material used for fluorescent leak detection is generally small, on the order of a few percent by weight of oil or less, a material can adversely affect the properties or performance of the oil or refrigerant to which it is added. In addition, conventional fluorescent materials have not always maximized visible light emission from UV excitation with respect to the amount of fluorescent material added.
Another drawback to current leak detection techniques is that conventional fluorescence leak detectors have used a very bright mercury vapor lamp with a UV filter. Commercial UV fluorescent leak detection devices also use halogen light sources. Other suitable UV light sources are disclosed Skoog, et al., Principles of Instrumental Analysis, Saunders College, 1980, Figure 5-2, p. 116, which lists components and materials for spectroscopic instruments and lists several light sources, including a xenon lamp, as a source of visible light.
Flashing UV light has been used for various applications in the past. Typically these applications use excited xenon in a light tube to provide continuous light or to provide UV energy for chemical curing reactions, such as in dental reconstruction. Up until our present invention, however, flashing UV light has not been recognized as beneficial for leak detection.
For example, U.S. Pat. No. 4,279,254 discloses a UV light used on medical patients to radiate the skin. The UV electrical light circuit, which is not battery operated, counts pulse flashes in order to automatically shut off and avoid over-exposure as a safety measure; U.S. Pat. No. 4,112,335 discloses a rapid pulse UV light apparatus in which a UV light source is fed as a high frequency pulse into a high pressure (3 atmosphere) xenon light tube to cure epoxy resin tooth caps; U.S. Pat. No. 4,550,275 discloses a high efficiency pulse light source as a xenon light source to excite lasers; U.S. Pat. No. 5,185,552 discloses a vacuum UV light source which provides a high output UV light source using low pressure hydrogen or deuterium in a hollow tube at wave lengths below 180 mm; U.S. Pat. No. 4,229,658 discloses a dental xenon light apparatus which supplies UV and visible light and is used to cure tooth restoration materials by focusing the light on a small area of a tooth; and U.S. Pat. No. 5,043,634 discloses a pulsed light source using a pulsed xenon light tube coupled with a phosphorus coating which emits different colors of visible light as a navigational aid.
Industries in which leak detection is important have not recognized that leaks can be detected by administering a fluorescing material to any system using a carrier fluid injected at any pressure, regardless of oil type, and detected using a UV lamp. Moreover, we are not aware that anyone prior to our invention recognized that a visible dye can be used in addition to a UV fluorescing material to further facilitate visualization and location of leaks. Our recognitions provide a much simplified and advantageous method of leak detection.
An object of the present invention, is to provide a more effective method of introducing an additive into a system to avoid the need for a system specific carrier oil and the time consuming process of replacing the filter to introduce the additive.
Another object of the present invention is to provide a method of introducing an additive into a system which will not degrade the performance of the system.
Another object of the present invention is to provide a method of introducing conventional fluorescent or daylight visible dyes or mixtures thereof into a fluid system for leak detection.
Still another object of the present invention is to provide a method of introducing a conventional material with heretofore unrecognized UV-fluorescing properties into a refrigeration oil or lubrication system using a carrier solvent, in which the solvent is later separated from the oil or lubricant after use as a carrier.
The materials having fluorescence properties in accordance with the present invention are usually solid at room temperature, and are selected from a group of commercially available compounds, some of which are already used in the oil manufacturing industry as additives to promote the performance characteristics of oil. Many of these fluorescent materials are also soluble in lubricants and oils, whether the oil is petroleum-derived (mineral) or synthetic but up until now their ability to fluoresce has not been appreciated.
A yet further object of the present invention is to select a carrier solvent which will evaporate from the compressor oil, so that it can be removed by adsorption with a filter-dryer of a refrigeration system. The solvent should generally be immiscible or slightly miscible in the refrigeration system oil or lubricant, so that it can be removed from the system by adsorption using appropriately sized filter-dryers containing an adsorbent which adsorbs the solvent similar to those used in conventional refrigeration system design. The solvent should also be compatible with the lubricants and refrigerants currently used by the HVAC industry. A carrier solvent for the additive is removed after being used as a carrier in accordance with the present invention and thus greatly reduces concerns of both material and refrigerant incompatibility of the carrier solvent with the system.
Another object of the present invention is to provide daylight visible or fluorescent additives which are soluble in both the solvent carrier as well as the various types of refrigerant oils, i.e. synthetic or petroleum-derived. Solubility is desirable for at least two reasons. First, the additive is dissolved in the solvent alone for delivery into the refrigeration or air conditioning system. If the additive were insoluble in the solvent, the additive could precipitate or form a residue. As a result, inadequate amounts of additive would be delivered into the system or insoluble residues could clog key system components, such as the expansion device, and cause operational problems. Second, once adequate amounts of the additive are delivered into the system, the additive must be soluble in the specific refrigerant lubricant used in the system, allowing the additive to travel with the lubricant throughout the system to the location of the leak. The refrigerant/lubricant/additive mixture then leaks into the atmosphere at the site of the leak, leaving a lubricant/additive residue at the site which can be detected by visible light or by application of UV light to the area.
Furthermore, another object of the present invention is to overcome the problems and disadvantages of conventional leak detecting light sources, which include power consumption and poor detection capabilities, by providing a high-efficiency xenon flashing light source. We have found that the advantage in using a flashing light instead of, for example, a continuous light source, is that it makes the fluorescing material more noticeable. That is, the flashing light provides the operator with a continuous comparison between a leaking region with fluorescence and the same region with normal ambient light, thereby making the fluorescing material appear to flash and easier to detect.
Normally, xenon lights inherently flash at a frequency so that the light is easily perceptible as continuous to the human eye. According to the present invention, however, the light has an adjustable on-off duty cycle, wherein the light may be off for 0.5 seconds or more. As a result of the longer off-time, such units use significantly less power and make battery powered units practical.
These objects have been achieved in accordance with the present invention by a method in which an additive is introduced with a carrier fluid into a refrigeration system to detect system leaks.
An advantage of the present invention is that it can also use known fluorescent dye materials. Instead of dissolving the material in an oil or petroleum-based carrier which has to be compatible with the oil used in the system, however, our invention is based on the recognition that the fluorescent material can be of a type which is dissolvable in a solvent carrier which does not remain in the system. The fluorescent materials and solvents of the present invention are, to great advantage, universally soluble and, at the same time, fluorescent in petroleum-based and synthetic oils and lubricants.
According to a currently preferred embodiment, the carrier fluid is a non-oil carrier, such as an alcohol. When the carrier is an oil or lubricant, as used in the past, additives such as fluorescing materials, which may or may not have performance enhancing properties, can have very low solubility. In contrast thereto, alcohol generally has a high solubility for such fluorescing materials of the present invention, and therefore, will dissolve the additive with a comparatively smaller volume as compared to the volume of oil or lubricant which might be necessary to dissolve the same quantity of additive.
The present invention also advantageously uses additives with natural fluorescent characteristics which are not damaging to the performance of the oil, lubricant or refrigerant. Moreover, with the use of our invention and its general principles, the incorporation of certain additives into the system actually benefits the performance, wear, stability, and/or life of the oil or lubricant when the additive has anti-wear, anti-oxidant, viscosity improving, and/or dispersing properties.
According to the present invention, the extent to which the additives are used is essentially only limited by the solubility of the additive in the system fluid. The concentration of additive should, generally speaking, be limited to an amount below which precipitation occurs, because precipitation of the additive may be detrimental to the fluid system and performance.
Yet another advantage of the present invention is the use of mixtures of fluorescent materials and daylight visible dyes which, when used together, provide enhanced visual detection of the leakage and/or alter the fluorescent color of the fluorescent material to enhance detection of the mixture.
In accordance with the present invention, a method is utilizable by which an additive and a solvent carrier can be introduced into a refrigerant system, regardless of the system pressure and temperature or whether the system is or is not open to the environment. The solvent carrier can then be removed from the system by adsorption in a filter normally present in the system, leaving only the dissolved additive in the system oil or lubricant.
In summary, we have discovered, among other things, that the carrier solvent should have the following properties to obtain the benefits of our invention:
1. The solvent must be capable of dissolving the additive; PA1 2. The solvent should ideally, but need not, be immiscible in all possible lubricants so that the solvent does not dissolve in the lubricant and become difficult to remove or reduce the lubrication properties of the lubricant; PA1 3. The solvent should be compatible with all materials and fluids in the system; and PA1 4. The solvent should be rapidly adsorbed by the molecular sieve, activated alumina, and/or carbon filter-dryers used in typical refrigeration systems so that the solvent can be removed from the system thereby leaving only the additive dissolved in the lubricant.
Xenon tubes used as a light source according to the present invention, advantageously produce a full spectrum of light very efficiently, without the generation of significant heat. This light can then be filtered to remove the visible and IR frequencies, leaving only the ultraviolet spectrum. The result is an intermittent, intense light of long wave ultraviolet black light or UV-A, typically in the 180 nm to 390 nm wavelength range of the electromagnetic spectrum.
Generally, the light sources for detecting fluorescing materials require a filter to filter-out visible light. Without a filter, the illumination of the fluorescing material is much less noticeable. Typically, the filter is a glass filter because the conventional continuous light source generates sufficient heat to damage inexpensive filters. According to the present invention, however, the xenon filter cooling effect advantageously results from a duty cycle in which there is a relatively slow on/off frequency.
Xenon light sources are generally in the form of xenon arc lamps, which burn continuously, or xenon flash tubes which are typically flashed at very high frequencies to approximate (i.e., appear to the naked eye as) a continuous light source. However, the present invention employs a xenon light which is turned on at a low frequency, with a very pronounced on and off cycle. Such xenon flashing lights generate significantly less heat and thus avoid potential safety concerns, reduce fabrication costs, and allow for the use of inexpensive plastic or glass lenses or the application of a UV filter material directly on the xenon bulb. Their utilization in leak detection of the type involved herein provides advantages not heretofore recognized.
Instead of using a continuous beam of UV light, it was found that, by introducing an intermittent (on/off duty cycle) UV light, the UV sensitive fluorescing material is more noticeable. The on/off UV light source allows a repeated comparison between the fluorescing leak indicator and the background, much like a flashing warning light is more noticeable to a driver at night. We also found that an adjustable flashing frequency allows the user to adjust the frequency to suit the user according to ambient light conditions. The intermittent light also advantageously consumes significantly less power, making possible the use of light-weight, low-cost, portable, battery-powered units.